1. Field Of The Invention
This invention relates to normally vented caps for fluid containers such as fuel tanks. The invention allows venting in both vacuum and pressure conditions during normal operation. When the tank is tipped or inverted, the venting system closes itself and restricts leaking of fluid unless the internal tank pressure builds to an undesirable level.
2. Description Of The Art
The fuel delivery systems of many internal combustion engines require the absence of vacuum or pressure. This is sometimes achieved by venting the fuel tank through a tortuous path in a cap to the outside atmosphere. However, these caps may allow fluid to spill from the tank when the system is tipped or inverted.
It is desirable to provide an improved cap of this type which is easy to manufacture, compact, and which provides improved handling of fluids when the tank is tipped. Most importantly, there is a need for a cap of this type which closes when tipped but can vent again even when tipped if internal vapor pressure threatens to reach a level which jeopardizes the integrity of the tank or the cap. This could occur, for example, if an overturned lawn mower were exposed to a heat source such as a muffler or direct sunlight. In this situation, it would be preferable to allow intermittent and brief venting in order to maintain the integrity of the tank and the cap, and to prevent excess vapor pressure discharge.